Rails - May 2011 - Database performance for polymorphic associations under high load

Hey guys,

I''ve been thinking lately about polymorphic associations, and I
wonder: is there a noticeable or tangible performance "hit" from doing
polymorphic associations when you''ve got your database under really
high query load?

So for example, maybe I have a "message" model, a "user"
model and an
"administrator" model, without any subclassing or STI going on.
Message has a polymorphic interface called "message_author", and both
"User" and "Administrator" use it.  Say there wind up being
~1 million
messages in that message table.  Assuming everything''s properly
indexed, do polymorphic associations add any significant overhead to
conducting database queries?

Thanks guys, appreciate the input.

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I would stay away from polymorphic as there is no way to enforce DB FK 
relationships.

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That''s been my "official" stance for a while as well, and
I''m fully
aware of that - but I''m also wondering about its performance, so I can
get a better perspective of the "full picture", if you follow my
logic.

Still, your point is quite valid and has been taken under advisement.
Thank you.

On May 2, 9:20 pm, Me <chabg...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I would stay away from polymorphic as there is no way to enforce DB FK
> relationships.
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